AWS ApiGateway with http type is not able to add secure service name while integration

Hi Team,

I am trying to create the API gateway with Http type with the integration of load balancer and existing domain.

While passing the map values on the integration block it gets error below,

"ANY /pws-fin-oversight-api/{proxy+}" = {
  connection_type    = "VPC_LINK"
     vpc_link           = "pws-vpc"
  integration_uri    = module.loadbalancers.listener-internal-https
  integration_type   = "HTTP_PROXY"
  integration_method = "ANY"
  authorization_type     = "CUSTOM"
  authorizer_key         = "lambda"


tls_config = {
      server_name_to_verify ="" 

│ The given value is not suitable for module.api_gateway.var.integrations declared at modules\apigateway\,1-24: Attribute types must all match for
│ conversion to map.

It is passing to different errors if we remove the tls block and then run the plan successfully.
But the requirement needs to pass the domain name to verify in tls block